In the semiconductor manufacturing process, with the development trend of ultra-large scale integrated circuits, feature dimensions of the integrated circuits continues to decrease. To accommodate the reduction of the feature dimensions, a channel length of a metal-oxide-semiconductor field effect transistor (MOSFET) decreases. However, as the channel length of the device decreases, a distance between a source and a drain of the device decreases. Therefore, control ability of a gate to the channel is degraded, and it is more and more difficult to pinch off the channel by the gate voltage. As a result, a subthreshold leakage phenomenon, also known as a short-channel effect (SCE), is more likely to occur.
Therefore, to better accommodate the reduction of the feature dimensions, the semiconductor process gradually began to transit from the planar transistor to a three-dimensional transistor having higher efficiency, such as a fin field effect transistor (FinFET). In the FinFET, the gate can control the ultrathin body (fin) from at least two sides. Thus, the FinFET has a much stronger gate-to-channel control ability than the planar MOSFET device, and can well suppress the short-channel effect. Compared to other devices, the FinFET has better compatibility with existing integrated circuit fabrication techniques.
However, the electrical performance of the conventional FinFET needs to be improved. The disclosed device structures and methods are directed to solve one or more problems set forth above and other problems.